Chapter 11 : Computer Science. Information Representation. Class XI ( As per CBSE Board) New Syllabus

Transcription

1 Chapter 11 : Computer Science Class XI ( As per CBSE Board) Information Representation New Syllabus

2 Introduction In general term computer represent information in different types of data forms i.e. number, character,picture,audio, video etc. Computers are made of a series of switches/ gates. Each switch has two states: ON(1) or OFF(0).That's why computer works on the basis of binary number system(0/1).but for different purpose different number systems are used in computer world to represent information. E.g. Octal, Decimal, Hexadecimal.

3 Decimal Number System Characteristics Positional (Most) people use the decimal number system Why? THIS A POSITIONAL NUMBER SYSTEM.and that's of great advantage..simple shifting the position of decimal.it become complex either case to use number system <10 or >10.

4 Binary Number System Characteristics Positional Most (digital) computers use the binary number system Why? Computers are made of a series of switches/ gates. Each switch has two states: ON(1) or OFF(0).That's why computer works on the basis of binary number system(0/1).

5 Decimal-Binary Equivalence

6 Binary Decimal Conversion Using positional notation

7 Decimal-Binary Conversion Using the Division Method: Divide decimal number by 2 until you reach zero, and then collect the remainders in reverse.

8 Hexadecimal Number System Characteristics Positional Computer programmers often use the hexadecimal number system,why? Computers only work on the binary number system. The hexadecimal number system is commonly used to describe locations in computer memory. They are also used in assembly language instructions.

9 Decimal-Hexadecimal Equivalence

10 Hexadecimal to decimal Decimal to hexadecimal Read from bottom to top: 25 16

11 Binary - hexadecimal

12 Binary to hexadecimal Convert to hex Starting at the right end, split into groups of 4: (pad empty digits with 0)

13 Hexadecimal to Binary Convert 3D9 16 to binary Convert each hex digit to 4 bits: leading zeros) (can remove

14 Octal Number System Characteristics Positional Computer programmers often use the octal number system,why? Octal and hex use the human advantage that they can work with lots of symbols while it is still easily convertible back and forth between binary.

15 Decimal-Octal Equivalence

16 Octal to decimal positional powers of 8: decimal positional value: Octal number:

17 Decimal to octal Using the Division Method: Example 1:

18 Binary-Octal Conversion E.g. Octal to binary

19 Representing Unsigned Integers Mathematics Computer programming

20 Representing Unsigned Integers

21 Adding Unsigned Integers Start at right column Proceed leftward Carry 1 when necessary

22 String representation String is any finite sequence of characters.any string includes etters, numerals, symbols and punctuation marks. Computers are designed to work internally with numbers. In order to handle characters, we need to choose a number for each character. There are many ways to do this

23 String representation Following are some form of character set ASCII UNICODE ISCII

24 String representation ASCII It is most common coding system (Pronounced ass-key). ASCII = American National Standard Code for Information Interchange It is Defined in ANSI document X It is a 7-bit code.its 8th bit is unused (or used for a parity bit) Two general types of codes: 95 are Graphic codes (displayable on a console) 33 are Control codes (control features of the console or communications channel)

25 String representation ASCII

26 String representation ASCII CHART LEAST SIGNIFICANT BIT

27 String representation ASCII Hello, world Example LEAST SIGNIFICANT BIT

28 String representation UNICODE It is a worldwide character-encoding standard.its main objective is to enable a single, unique character set that is capable of supporting all characters from all scripts, as well as symbols, that are commonly utilized for computer processing throughout the world.

29 String representation VARIOUS UNICODE ENCODING Name UTF-8 UTF-16 UTF-32 Smallest code point Largest code point 10FFFF 10FFFF 10FFFF Code unit size 8 bits 16 bits 32 bits Byte order N/A <BOM> <BOM> Fewest bytes per character Most bytes per character LEAST SIGNIFICANT BIT

30 String representation UTF-8 It is most popular type of Unicode encoding. It uses one byte for standard English letters and symbols, two bytes for additional Latin and Middle Eastern characters, and three bytes for Asian characters Any additional characters can be represented using four bytes It is backwards compatible with ASCII, since the first 128 characters are mapped to the same values. LEAST SIGNIFICANT BIT

31 String representation LEAST SIGNIFICANT BIT

32 String representation UTF-32 It is a multi-byte encoding that represents each character with 4 bytes * Makes it space inefficient Its main use is in internal APIs where the data is single code points or glyphs, rather than strings of characters Used on Unix systems sometimes for storage of information LEAST SIGNIFICANT BIT

33 String representation UTF-32 It is a fixed length encoeding scheme that uses exactly 4 bytes to represent all Unicode code points.e.g. Letter A [U+41] LEAST SIGNIFICANT BIT

34 String representation ISCII ISCII stands for Indian Script Code for Information Interchange for Indian languages. It is an 8-bits code to represent Indian scripts. The Department of Electronics (DOE) has established standard and standard are in action from These codes are used for 10 Indian scripts- Devanagri, Punjabi, Gujrati, Udia, Bengali, Asami, Telgu, Kannad, Malayalam and Tamil. C-DAC (established in August- September, 1988) developed standard for font coding in 1990 is called ISFOC (Indian Standards for Font Coding). LEAST SIGNIFICANT BIT